In model tests in the aspect of the geotechnical engineering, the studies on the internal transformation law and mechanism of soil bodies are of great significance on the research of the problem inherence of the geotechnical engineering. Particularly, the area of perennial frozen soil, seasonal frozen soil and temporary frozen soil regions on earth approximately accounts for 50% of the land area, wherein the distribution area of perennial frozen soil is 35,000,000 km2, approximately accounting for 20% of the land area. And there are great difference between the engineering characteristics of frozen soil and those of conventional soil, hence, it is very implant to develop the study on the engineering characteristics of frozen soil and the characteristics of a constructed object in a frozen soil region.
The patent with the patent number of 201110074794.2, and the invention title of A Method for Preparing High-Water Content Frozen Soil Sample disclosed a technical method for preparing a high-water content frozen soil sample by utilizing conventional equipment, the method could prepare a high-ice content frozen soil sample according to actually required dimensions, and based on the prepared frozen soil sample, a soil testing instrument was used to test the engineering characteristics of the frozen soil.
However, conventional soil body deformation measurement method is to embed a series of sensors inside the soil body, and obtain the displacements of some discrete points, the sensors are easily subjected to the effect due to the disturbance of the external environment, the measurement result often are not accurate, and the whole displacement field in continuous deformation inside the soil body can not be presented as well; and the embedment of the sensors also generate disturbance on the real soil body environment. Modern digital image technologies are only limited to measure the macroscopic or boundary deformation of the soil body as well, and can not realize the visualization of the internal deformation of the soil body; and although X-ray, γ-ray, computer assisted tomographic scanning (CAT scanning) and magnetic resonance imaging technology (MRI) can be used for measuring the continuous deformation inside the soil body, and expensive expenses limit wide application of these technologies. Artificial synthesis of transparent soil in combination with optical observation and image processing techniques is utilized to realize the visualization of the internal deformation of the soil body, with low expense, and simple operation. However its precondition is to obtain an artificially synthesized transparent soil with high transparency, and the properties similar to the natural soil body. At present, different materials were adopted to prepare transparent soil, and some achievements were obtained, for example:
document 1: Allersma, H. G B., 1982, “Photo-Elastic Stress Analysis and Strains in Simple Shear,” Proceedings, IUTAM Symposium on Deformation and Failure of Granular Materials, Delft, edited by P. A. Vermeer and H. J. Luger, pp. 345-353.
In document 1, in 1982, Allersma put forward that a mixture of a broken glass (with the refractive index of 1.4738) material and a liquid with the same refractive index was used, for preparing a transparent soil.
document 2: Iskander, M., Lai, J., Oswald, C., and Mainnheimer, R., 1994, “Development of a Transparent Material to Model the Geotechnical Properties of Soils,” Geotech. Test. J., Vol. 17(4), pp. 425-433.
document 3: Iskander, M., Liu, J., and Sadek, S., 2002a, “Optical Measurement of Deformation Using Transparent Silica Gel to Model Sand,” Int. J. Phys. Modell. Geotech., Vol. 2(4), pp. 27-40.
document 4: Iskander, M., Liu, J., and Sadek, S., 2002b, “Transparent Amorphous Silica to Model sand soil,” J. Geotech. Geoenviron. Eng., Vol. 128(3), pp. 262-273.
document 5: Liu, J. Y., Iskander, M., and Sadek, S., 2003, “Consolidation and Permeability of Transparent Amorphous Silica,” Geotech. Test. J., Vol. 26(4), pp. 390-401.
In documents 2-5, in 1998, and 2002, Iskander et al utilized industrially produced amorphous silica powder or gel (with the refractive index of 1.447) and a pore fluid with corresponding refractive index to prepare an artificially synthesized transparent soil.
document 6: Wu Mingxi, 2006, Study on synthetic transparent soil and its triaxial test [D], Magisterial thesis, Dalian, Dalian University of Technology, pp. 18-21.
document 7: Sui Wanghua, Gao Yue. Status and prospect of transparent soil experimental technique[J], Journal of China Coal Society, 36(4): 577-582.
document 8: Cao, Z. H., Liu, J. Y, and Liu, H. L., 2011, “Transparent Fused Silica to Model Natural Sand,” Pan-Am CGS Geotechnical Conference.
document 9: Ezzein, F. M., and Bathurst, R. J., 2011, “A Transparent Sand for Geotechnical Laboratory Modeling,” Geotech. Test. J., Vol. 34(6), pp. 590-601.
document 10: Guzman, I. L., Iskander, M., Suescun-Florez, E., and Omidvar, M., 2013, “A Transparent Aqueous-Saturated Sand Surrogate for Use in Physical Modeling,” Acta Geotechnica, published on line, July 2013.
http://link.springer.com/article/10.1007%2Fs11440-013-0247-2
In documents 6-10, in 2006, 2013, etc., Wu Mingxi et al utilized fused quartz sand (with the refractive index of 1.4585) and a liquid with corresponding refractive index such as mixed oil or a calcium bromide solution to prepare an artificially synthesized transparent soil.
Existing technical data show that, solid particles for preparing transparent soil mainly adopt quartz materials, with the refractive index themselves of the solid particles between 1.44-1.46, and adopt borosilicate glass materials, with the refractive index themselves of the solid particles between 1.46-1.48, which is far higher than the refractive index of water of 1.33 and that of ice of 1.31. Hence, the utilization of existing solid particles for preparing transparent soil is incapable of preparing a saturated transparent frozen soil sample.
The fluorine-containing polymer is Teflon AF 1600 produced by American DuPont Company, with the refractive index of 1.31, and the density of 2.1-2.3 g/cm3; and it has the characteristics of high temperature resistance, low temperature resistance, chemical corrosion resistance, no viscosity, no toxicity, no pollution, high transparency and low refractive index, and also has the characteristics of gas permeability structure, hydrophobicity and chemical inertness, and has good similarity with the properties of the natural soil body. Teflon AF 1600 can be dissolved in fluorine solvents, and can be formed into a film or formed by melting and compression; and at present, it is mainly used in coating and impregnation or made into fibers, and the prepared liquid core also has application in various fields of absorption, fluorescence, Raman spectral analysis, gas sensors and the like. And the application of Teflon AF 1600 in the preparation of transparent frozen soil is yet not reported.